Lior Medina

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Verified

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• Ph.D. in Mechanical Engineering
• Senior Lecturer at Tel Aviv University

The symmetric and asymmetric buckling of an initially curved micro beam subjected to an axial prestressing load and transversal distributed electrostatic force is studied. The analysis is based on a reduced order (RO) model resulting from the Galerkin decomposition with buckling modes of a straight beam used as the base functions. The criteria of s...

The criterion defining the geometric parameters guaranteeing bistable behavior of electrostatically actuated curved axisymmetric circular plate is established. The usage of Berger’s approximation for von-Kármán nonlinear plates, combined with single degree of freedom (DOF) reduced order (RO) modeling, allowed derivation of a simple semi-analytical...

The symmetric snap-through response of a bistable structure, composed from two beams that are coupled via a rigid truss at their midpoint, is studied when subjected to a distributed electrostatic load. Both beams are double clamped and initially curved. The analysis is based on a reduced order (RO) model, resulting from Galerkin’s decomposition. Fo...

Kirigami structures provide a promising approach to transform flat films into 3D complex structures that are difficult to achieve by conventional fabrication approaches. By designing the cutting geometry, it is shown that distinct buckling‐induced out‐of‐plane configurations can be obtained, separated by a sharp transition characterized by a critic...

A curved bistable micro-beam, subjected to electrostatic loading from an electrode facing its concave side, may produce a snap-through response with voltages as low as 54%, when compared to actuation from a convex facing electrode. Such actuation has been dubbed “bow actuation” due to the similarity of preloading an arrow onto a bow, and the result...

The study of electrostatically actuated microplates in the presence of a mechanical pressure can further their usage as static pressure/mass sensors. The study was carried out using the Föppl-von-Kármán plate model, from which a reduced order (RO) model was derived that includes both loadings. Bistability criteria were extracted semi-analytically u...

A curved bistable micro-beam, subjected to electrostatic loading from an electrode facing its concave side, may produce a snap-through response with almost half the voltage when compared to actuation emanating from an electrode facing the convex side of the beam. Such actuation has been dubbed “bow actuation” due to the similarity of preloading an...

In this study, a set of criteria, which defines the appearance of dynamic bistability in curved beams is formulated and validated. Such a form of bistability can appear in curved microstructures when subjected to nonlinear, displacement-dependent, electrostatic load, prompting three limit points, but with an orientation that will not allow for a sn...

In the present study, an expanded dynamic model of an electrostatically actuated double beam metastructure, composed of geometrically different beams, is formulated and solved. The two beams are connected via an elastic bridge in the form of a linear spring, forming a weak coupling. A reduced order (RO) model is derived using Galerkin’s decompositi...

Following increasing interest in electrostatic actuation of curved beams via curved electrodes. A rigorous limit point analysis is carried out to view how the beam reacts as a function of its geometry, as well as that of the electrode. The culmination of the study is in a bistability condition that describes what geometry both beam and electrode mu...

The effects of membrane load on the axisymmetric bistable behaviour of circular curved micro plates is studied via axisymmetric reduced order (RO) models, incorporating radial prestress. One model is based on the Kirchhoff hypothesis and Föppl-von-Kármán's kinematics, while the second is based on Berger's approximated plate theory. The models are f...

The study brings forth extended criteria for electrostatically actuated micro-plates, which take into account the presence of prestress. Following previous studies that analysed the veracity of a reduced order (RO) model, based on Berger’s plate approximation, we present here an analysis of a single degree-of-freedom (DOF) model. The resulting simp...

A stability study of a micro-meta-structure (MMS), composed of two double clamped, initially curved micro beams, coupled via a rigid truss at their respective centres, is studied via a reduced order (RO) model when subjected to a distributed electrostatic load. The study is based on the energy method and Lyapunov stability analyses, carried out in...

The effect of membrane load on the behaviour of axisymmetric bistable circular curved microplates on Berger’s based axisymmetric reduced order (RO) model, incorporating radial prestress, is studied. The model is first validated for a “mechanical” load, against a Föppl-von-Kármán’s RO model with twenty degrees of freedom (DOF), a finite differences...

A limit point behaviour analysis of a metastructure, composed of two double clamped, initially curved beams, coupled via a rigid truss at their respective centres, is carried out when subjected to a distributed electrostatic load. The analysis is based on a reduced order (RO) model resulting from Galerkin’s decomposition, with symmetric buckling mo...

Electrostatically actuated, bistable, curved micromechanical beams can exhibit latching, wherein the beams remain in two distinct stable states without an applied voltage. These structures could serve as building blocks in a variety of applications such as micromechanical logic elements, switches, non-volatile memories, and low power consumption se...

A limit point behaviour of a metastructure, composed of two double clamped, initially curved beams, coupled via a rigid truss at their respective centres, is studied when subjected to a distributed electrostatic load. The analysis is based on a reduced order (RO) model, resulting from Galerkin’s decomposition, with symmetric buckling modes used as...

In article number 2005275, Horacio D. Espinosa, Daniel Lopez, and co‐workers demonstrate the engineering of nanoscale kirigami structures exhibiting a range of buckling‐induced controllable 3D configurations. By combining nanomanufacturing, in situ microscopy experimentation, and computational modeling, symmetric and asymmetric 3D configurations re...

Kirigami with a variety of cut patterns have been recently investigated as means to transform 2D surfaces into 3D structures offering a number of functionalities. In this work, we show that a single Kirigami motif, defining two inner panels connected by hinges, can generate a rich variety of out-of-plane symmetric and asymmetric deformation modes....

Traditional fabrication techniques are not suitable for the manufacturing of three-dimensional micro-scale structures. In this work, we report on a modified self molding punch-less sheet forming technique allowing fabrication of initially curved, non-planar, shallow micro shells. These structures, when appropriately configured, may exhibit the coex...

To induce snap-through (ST) switching in an electrostatically actuated bistable latchable curved micro beam, a close gap electrode facing the concave surface of the beam is commonly used. In the framework of an alternative architecture considered here, the electrode is placed in front of the convex (backward), rather than concave (forward) side of...

Curved bistable beams subjected to transverse loading may exhibit latching, namely remain in their buckled state under zero force. Under such circumstances, an opposite force is required for snapping-back (release) of the beam to its initial configuration. For an electrostatically actuated beam, two electrodes located at either side of the beam may...

Nano-mechanical resonators make exquisite force sensors due to their small footprint, low dissipation, and high frequencies. Because the lowest resolvable force is limited by ambient thermal noise, resonators are either operated at cryogenic temperatures or coupled to a high-finesse optical or microwave cavity to reach sub aN Hz-1/2 sensitivity. He...

In accordance with various embodiments of the present invention, mechanical systems incorporating movable microelectromechanical (MEMS)-based features, eg, cantilevers or suspended micron-and submicron-scale beams are utilized to secure solid-state devices such as controllers, microcontrollers, central processing units (CPUs), solid-state storage d...

Bistable micro devices are distinguished by their ability to stay in two different configurations under the same loading. Micro- and nanoelectromechanical systems (MEMS/NEMS) incorporating bistable elements are advantageous in a variety of applications, ranging from electrical and optical switches, to variable capacitors, nonvolatile memories, and...

We present a concept and a theoretical feasibility study of a sub g threshold inertial micro sensor, which incorporates a curved bistable beam as a suspension element. For certain range of geometric parameters such a beam can exhibit lathing, namely remain in its switched configuration at zero actuating force. Since the device can be released from...

Curved bistable beams subjected to transverse loading may exhibit latching, namely remain in their buckled state under zero force. Under such circumstances, an opposite force is required for snapping-back (release) of the beam to its initial configuration. For an electrostatically actuated beam, two electrodes located at either side of the beam may...

Curved micromechanical beams are a versatile platform for exploring multistable behavior, with potential applications in mechanical based logic elements and electrical and optical switches. Here we demonstrate bidirectional electrostatic actuation of a bistable, latched, micromechanical beam by the same electrode, which was used for the snap-throug...

Micro- and nanolectromechanical systems (MEMS/NEMS) incorporating two-dimensional structural elements such as plates attracted significant interest in recent years. In this work, we explore implementation of a model based on Berger's approximation, which significantly simplifies the formulation of a curved plate and describes it by a single governi...

Micro- and nanolectromechanical systems (MEMS/NEMS) incorporating two-dimensional structural elements such as plates and shells attracted significant interest in recent years. These structures demonstrate rich electromechanical behavior and could be advantageous in applications. In this work, we explore implementation of two models describing axisy...

Curved beams subjected to transverse force may exhibit latching phenomena, namely remain in the buckled configuration under zero force. In this study we investigate the latching in bistable electrostatically actuated initially curved and prestressed beams. The analysis is based on a reduced order (RO) model resulting from the Galerkin decomposition...

We demonstrate an open-loop self-excitation response in a curved, bistable microelectromechanical beam under a time-independent electrostatic load. The self-excitation is triggered by placing a high value resistor in series with a beam that is on the verge of bistability. The voltage deflection curve of such a beam contains an inflection point, whe...

The axisymmetric snap-through of an initially curved circular micro plate, subjected to a transversal distributed electrostatic force is studied. The analysis is based on a reduced order (RO) model resulting from the Galerkin decomposition, with buckling modes of a flat plate used as the base functions. In order to check the validity of the RO mode...

The axisymmetric snap-through of an initially curved circular micro plate, subjected to a distributed electrostatic force is studied. The analysis is based on a reduced order (RO) model resulting from the Galerkin decomposition, with buckling modes of a flat plate used as the base functions. The results of the RO model are compared with the results...

We demonstrate dynamic snap-through from a primary to a secondary statically inaccessible stable configuration in single crystal silicon, curved, doubly clamped micromechanical beam structures. Nanoscale motion of the fabricated bistable micromechanical devices was transduced using a high speed camera. Our experimental and theoretical results colle...

In this work, the results of numerical investigations of the transient dynamics of a stress-free initially curved bistable double clamped micro beam actuated by a suddenly applied electrostatic force are presented. The analysis is based on a reduced order (RO) model derived through the Galerkin decomposition. Two beam configurations and two corresp...

Curved beams subjected to transverse force may exhibit a latching phenomena, namely remain in their buckled configuration under zero force such that an opposite force is required for their release. In this study, we investigate the latching in bistable electrostatically actuated prestressed curved beams. The analysis is based on a reduced order (RO...

We report on a first experimental demonstration of dynamic trapping of electrostatically actuated double clamped curved micro beam. The beam is configured in an isolated singular post-buckled configuration, showing enhanced gap usage which cannot be reached by either static or by a suddenly applied single step load. The trapping is achieved using a...

Micro and nano devices incorporating bi-stable structural elements such as micro beams are designed to exploit the fact that the latter possess two stable configurations at the same actuation force. Generally, the transition of a micro beam from one table state to another, namely the snap-through which is essentially dynamic phenomenon, can be init...

The symmetric and asymmetric buckling of curved micro beams subjected to distributed electrostatic force is studied. The analysis is carried out for two separate cases: a case of a stress-free beam, which is initially curved by fabrication and a case of a pre-stressed beam buckled due to an axial force. The analysis is based on a reduced order (RO)...

The asymmetric buckling of curved micro beams subjected to nonlinear deflection-dependent electrostatic load is studied. The analysis is preformed for two separate cases, a case in which the beam is initially curved by means of fabrication and thus stress-free, and a case in which the curvature of a beam is generated due to buckling under an axial...

The asymmetric buckling of a shallow initially curved stressfree micro beam subjected to distributed nonlinear deflectiondependent electrostatic force is studied. The analysis is based on a two degrees of freedom reduced order (RO) model, resulting from the Galerkin decomposition with linear undamped eigenmodes of a straight beam used as the base f...

The asymmetric buckling of a shallow initially curved stress-free micro beam subjected to distributed nonlinear deflection-dependent electrostatic force is studied. In order to highlight the symmetry breaking phenomenon and the approach to its analysis, the subsidiary simplified problem of a curved beam attached to a linearly elastic foundation, an...